I. Field of the Present Invention
The present invention relates generally to motor vehicle suspension systems, and more particularly to a leaf spring construction for use in motor vehicles.
II. Description of the Prior Art
Many previously known motor vehicles suspension systems include leaf springs for resiliently suspending an axle housing or other means for rotatably supporting a vehicle wheel with respect to the frame of the vehicle. Often, the spring comprises a plurality of flat leaf springs with a rectangular ribbon-type shape. The spring is resiliently biased to form a semi-elliptical shape wherein the central portion of the spring is resiliently biased outwardly from the ends of the spring, and the resiliency is maintained by stacking a greater number of leaves at the center of the spring than at each end of the spring. While such a spring is well adapted for resilient deflection normal to the plane of the spring leaves, the length of the spring is typically much greater than the width of the spring leaves. As a result, lateral forces which can be exerted upon the wheel relative the the frame, such as centrifugal forces encountered during cornering, can cause the spring to deflect laterally and thus disorient the wheels from a desired stable position with respect to the frame.
One previously known means for restricting lateral displacement of the wheel due to lateral deflection of the spring comprises the installation of supports which restrict such movements. For example, radius rods, track bars and the like are secured to and between a suspended component and a fixed vehicle structure such as a framing member. However, such members can reduce the ground clearance of the vehicle since they must clear the drive train extending beneath the vehicle. Alternatively, the supports can be specially configured to extend around protruding components whereby the support is particularly configured for use with only one particular type of automobile. Thus, the manufacturing of such supports is subject to substantial expense for a wide range of vehicles. Moreover, even if a particular support can be applied to a wide variety of vehicles, such supports are often made of steel or other heavy metals, thus increasing the weight of the vehicle. Furthermore, such members and their connections with the automobile, are subject to wear and corrosion such that they may become ineffective and must be replaced in addition to normal replacement of the other suspension components.
One previously known means for strengthening the spring itself is shown in U.S. Pat. No. 3,975,005 to Duchemin. That patent discloses a spring leaf construction in which the leaf is formed from a bar having a circular cross-section at its center and a progressively flattened cross-section toward each end. While such a spring leaf construction provides a substantial amount of strength at the center of the leaf, and thus avoids the need for stacking a plurality of flat leaf springs together, the cylindrical center portion of the spring is narrower than the longitudinal ends of the spring and also subject to lateral deflection when subjected to lateral forces.
U.S. Pat. No. 2,654,597 to Barenyi discloses a flat leaf spring having a rhombus shape. Such a leaf spring has a widened central zone which is received in a correspondingly shaped groove in a support member which is then secured to a framing member of the vehicle for fixedly entraining the spring against lateral deflection. However, the patent teaches that this suspension construction permits the frame to resist lateral deflection of the spring leaf, and the correspondingly grooved support member is an important feature of the invention of Barenyi. As a result, the patent does not teach or suggest the formation of a leaf spring whose shape inherently resists lateral deflection between the ends of the leaf.